UVC reflective coating

ABSTRACT

The present disclosure provides an ultraviolet light-C (UVC) reflective coating composition. The UVC reflective coating includes a polymer binder of a first volume having a first refractive index and an inorganic material of a second volume having a second refractive index at least 0.2 greater than the first refractive index, the second volume in ratio to the first volume such that the reflective coating is at or below critical pigment volume concentration (CVPC), wherein the reflective coating is configured to diffusely reflect at least 10% UVC.

CLAIM OF PRIORITY

This application is a continuation of U.S. application Ser. No.14/071,889, filed Nov. 5, 2013, which claims priority to U.S.Provisional Patent Application Ser. No. 61/722,238, filed Nov. 5, 2012,each of which are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates generally to compositions of coatingswhich reflect ultraviolet light, including ultraviolet-C (UVC), moreparticularly, UVC reflecting polymer-binder coating compositions whichare below the critical pigment volume concentration (CPVC).

BACKGROUND

Reflective surfaces can include metals, plastics, and the like.Non-reflective surfaces can be coated with a light reflective coating soas to effectively make the surface light reflective. Light reflectivecoatings, such as paint, can be used for a number of differentapplications. For example, a light reflective coating can be used toprovide aesthetic benefits or energy saving benefits. Specific types oflight reflective coatings, such as a UVC reflective coating can be usedto increase the effectiveness of UVC-emitting light sources for severalapplications, including, but not limited to, disinfecting surfaces orrooms (e.g., a hospital room or a clean room), decontaminatingwastewater, catalyzing a desired chemical reaction, oxidizing a volatileorganic compound, or the like.

U.S. Pat. No. 3,956,201 and U.S. Pat. No. 5,892,621 teach fluorinatedpolymers and air void morphologies to scatter a broad spectrum of light.

U.S. Pat. No. 7,511,281 teaches an Ultraviolet Germicidal irradiation(UVGI) sterilization process.

U.S. Pat. No. 3,300,325 teaches air-void filled coating compositions forUVA and UVB reflecting paint.

SUMMARY OF THE INVENTION

The present inventors have recognized, among other things, that aproblem to be solved can include providing a coating capable ofreflecting UVC at about 254 nanometers. Metals, plastics, or paints canbe UVC-absorbing. Current coatings configured to reflect ultravioletlight typically scatter UVA or UVB light but absorb UVC. In an example,the present subject matter can provide a solution to this problem, suchas by a coating composition configured to diffusely reflect at least 10%UVC at about 254 nanometers (nm).

The inventors have determined, amongst other things, that a problem tobe solved includes providing a coating, including a pigment, configuredto reflect (e.g., not absorb) UVC light. Common previous approachestypically used titanium dioxide, which can be UVC absorbing. Forexample, interior paints typically utilize titanium dioxide as theprimary light scattering pigment and as such, absorb approximately 93%to 97% percent of the UVC light and typically reflect 3% to 7% of theUVC light. In an example, the present subject matter can provide asolution to this problem, such as by providing a coating including aninorganic material configured to reflect UVC light, such as at leastabout 10% of incident UVC light.

The present inventors have recognized, among other things, that aproblem to be solved can include providing a UVC reflective coatingcapable of being used in a harsh environment. Harsh environments caninclude, for example, a hospital or wastewater or air disinfectionreactor, wherein coatings can be subjected to staining, abrasion,damaging chemicals, or water. In an example, the present subject mattercan provide a solution to this problem, such as by providing a coatingat or below critical pigment volume concentration, such that the presentUVC reflective coating can be less susceptible to such harsh conditions.That is, the present coating, in an example, is not a void coating.

DETAILED DESCRIPTION

Reference will now be made in detail to certain claims of the invention,examples of which are illustrated in the accompanying drawings. Whilethe invention will be described in conjunction with the enumeratedclaims, it will be understood that they are not intended to limit thoseclaims. On the contrary, the invention is intended to cover allalternatives, modifications, and equivalents, which can be includedwithin the scope of the invention as defined by the claims.

References in the specification to “one embodiment,” “an embodiment,”“an example embodiment,” and the like, indicate that the embodimentdescribed can include a particular feature, structure, orcharacteristic, but every embodiment may not necessarily include theparticular feature, structure, or characteristic. Moreover, such phrasesare not necessarily referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with an embodiment, it is submitted that it is within theknowledge of one of ordinary skill in the art to affect such feature,structure, or characteristic in connection with other embodimentswhether or not explicitly described.

Values expressed in a range format should be interpreted in a flexiblemanner to include not only the numerical values explicitly recited asthe limits of the range, but also to include all the individualnumerical values or sub-ranges encompassed within that range as if eachnumerical value and sub-range is explicitly recited. For example, arange of “about 0.1% to about 5%” or “about 0.1% to 5%” should beinterpreted to include not just about 0.1% to about 5%, but also theindividual values (e.g., 1%, 2%, 3%, and 4%) and the sub-ranges (e.g.,0.1% to 0.5%, 1.1% to 2.2%, 3.3% to 4.4%) within the indicated range.

In this document, the terms “a,” “an,” or “the” are used to include oneor more than one unless the context clearly dictates otherwise. The term“or” is used to refer to a nonexclusive “or” unless otherwise indicated.In addition, it is to be understood that the phraseology or terminologyemployed herein, and not otherwise defined, is for the purpose ofdescription only and not of limitation. Any use of section headings isintended to aid reading of the document and is not to be interpreted aslimiting; information that is relevant to a section heading may occurwithin or outside of that particular section. Furthermore, allpublications, patents, and patent documents referred to in this documentare incorporated by reference herein in their entirety, as thoughindividually incorporated by reference. In the event of inconsistentusages between this document and those documents so incorporated byreference, the usage in the incorporated reference should be consideredsupplementary to that of this document; for irreconcilableinconsistencies, the usage in this document controls.

The term “about” as used herein can allow for a degree of variability ina value or range, for example, within 10%, within 5%, or within 1% of astated value or of a stated limit of a range. When a range or a list ofsequential values is given, unless otherwise specified any value withinthe range or any value between the given sequential values is alsodisclosed.

The term “substantially” as used herein refers to a majority of, ormostly, as in at least about 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%,98%, 99%, 99.5%, 99.9%, 99.99%, or at least about 99.999% or more.

The term “multiple” refers to two or more (e.g., 2, 3, 4, 5, 6, etc.).

The term “binder” refers to any material or substance that holds ordraws other materials together to form a cohesive whole.

The term “pigment” refers to a substance that imparts opacity, coloringor aesthetic appearance to the coating. Generally, a coloring pigment isa material that changes the color of reflected or transmitted light asthe result of wavelength-selective absorption. This physical processdiffers from fluorescence, phosphorescence, and other forms ofluminescence, in which a material emits light. That is, coloringpigments appear to be colored because they absorb some wavelengths oflight more than others. One or pigments can be employed in themanufacture of the coating described herein, such that the thin coatinghas a desired color. Suitable colors include, for example, black,yellow, blue, green, pink, red, orange, violet, indigo, brown, and anycombination therein. Generally, an opacifying pigment, which impartswhiteness, is a material that imparts opacity in a coating by lightscattering due to index of refraction differences between the opacifyingpigment and another material in the coating, such as a binder or airvoids.

The term “UVGI” refers to Ultraviolet Germicidal Irradiation, such as acommon process used to control the spread of dangerous microbes.

The term “ultraviolet light” refers to electromagnetic radiation with awavelength shorter than human-visible light, such as about 10 nm toabout 400 nm.

The term “UVC” (e.g., ultraviolet C, short-wave Ultraviolet, FAR-UV,deep UV) refers to the band of UV light between about 100 nm and about280 nm. Further, a subset of UVC includes, UV light lying between thewavelengths of about 200 and about 300 nm, commonly referred to as the“germicidal region” because UV light in this region can be lethal tomicroorganisms including, but not limited to, bacteria, protozoa,viruses, molds, yeasts, fungi, nematode eggs, or algae. An especiallydestructive wavelength of UV light is about 260 nm. Germicidal UV lampstypically emit light with a wavelength that is substantially close to260 nm for its destructive purposes, such as around typically around 254nm.

The term “absorbing” refers to the process by which a photon isprevented from transmitting through, refracting, or reflecting from amaterial.

The term “PVC” refers to Pigment Volume Concentration, or the totalvolume percentage of pigment in a coating system after it has dried,cured or otherwise been applied such that diluents or solvents haveevaporated, and intended physical or chemical changes have occurred.

The term “CPVC” refers to Critical Pigment Volume Concentration, or thepoint at which there is sufficient binder present to at least partiallycover each pigment particle and fill most voids between particles.

As used herein, “greater than CPVC” refers to pigment concentrationswhere the pigments become difficult to fully wet so as to beencapsulated by the binder. That is, pigment particles can be touchingso as to provide a system with air voids, poor stain resistance, poorrub resistance, low gloss, or reduced material properties.

The term “less than CPVC” refers to pigment concentrations where thepigment particles remain at least partially to substantially fullywetted or encapsulated by the binder. That is, the binder is able tofill most voids between pigment particles.

The term “void coating” refers to a greater than CPVC coating whereopacity is achieved by the index of refraction difference imparted byair voids.

The term “non-void coating” refers to a less than CPVC coating wherelarge scale air-voids are not present.

The term “human-visible” refers to optical properties of an object orprocess that occurs within the range of human vision, typically fromabout 400 to about 700 nanometers in wavelength.

The term “transparent” refers to a photon traveling through a materialwithout being absorbed.

The term “light” refers to any form of electromagnetic radiation.

The term “specular reflection” refers to mirror-like reflection of lightfrom a surface, in which light from a single incoming direction isreflected into a single outgoing direction.

The term “light scattering”, “diffusively reflect”, or “diffusereflection” refers to reflection of light from a surface or sub-surfacesuch that an incident ray is reflected or scattered at many anglesrather than at just one angle as in the case of specular reflection.

The term “oxide” refers to binary compound of oxygen and an element,including a single oxide, a dioxide, and a trioxide. For example, ametal oxide can include the metal with a single oxygen atom, two oxygenatoms, or three oxygen atoms.

The term “coating” refers to a layer or film applied to a substrate.

The term “particle size” refers to an average particle diameter.

The present disclosure describes a UVC reflective coating including apolymer binder of a first volume having a first refractive index and aninorganic material of a second volume having a second refractive indexat least 0.2 greater than the first refractive index, the second volumein ratio to the first volume such that the reflective coating is at orbelow critical pigment volume concentration (CVPC), wherein thereflective coating is configured to diffusely reflect at least 10% UVCat about 254 nanometers (nm).

Polymer Binder

Binders can include synthetic or natural resins such as alkyds,acrylics, vinyl-acrylics, vinyl acetate/ethylene (VAE), polyurethanes,polyesters, melamine resins, epoxy, or oils. Binders can be categorizedaccording to the mechanisms for drying or curing. Drying may refer toevaporation of the solvent or thinner, but it often refers to oxidativecross-linking of the binders and is indistinguishable from curing. Somecoverings, such as paints, form by solvent evaporation only, but manyrely on cross-linking processes.

The inventors have determined that many polymer backbone chemistriesused for transparent and opaque coatings, such as manypolyurethane-based compositions, can contain UVC absorbing molecularstructures. For example, acrylic chemistries are generally considered tobe UV transparent, but in the UVC wavelengths acrylic chemistries canbecome partially UVC absorbing, especially towards 254 nm. To mitigateinherent UVC absorption in a binder, the coating can be formulated tofilm-form as a thin layer. According to the present disclosure,preferred binder chemistries can at least partially avoid carbon tocarbon conjugations such as nitroethene, acyclic diene, heteroannulardiene, homoannular diene, enimine, and triene as they can contain UVCabsorbance bands between 215 to 260 nm; aromatics, such as benzene, asit can have an absorbance band at 256 nm, and carboxyl, phenol, andnaphthalene aromatex can have a UVC absorbance band from 220 to 280 nm;or other organic compound bond structures with UVC absorption.

In an example a polymer binder can include an organic binder. Polymerbinders can include aliphatic compounds, including alkanes, alkenes, oralkynes. In an example, the polymer binder can include a monomer with asmall pendant group or pendant atom with bond dissociation energies,including, but not limited to, of carbon to fluorine bonds at about 450kJ/mole or carbon to hydrogen bonds at about 410 kJ/mole. For example,monomers with 1, 2, or all 4 pendant groups around the sigma bond ofnon-chlorine halogenated elements possess strong relatively un-reactivebonds suitable for polymers to be used as binders for the UVC reflectingcoatings. For example, the polymer binder can include monomers withhalogenated elements. The polymer binder can include at least onefluorinated long chain addition polymer comprised of at least onemonomer having at least one fluorine atom attached to a carbon chainform. In an example, the polymer binder includes polyvinylidenefluoride.

In another example, the polymer binder can include a monomer withacetate or acrylic and other common pendant groups in at least partialor full replacement of hydrogen or halogen pendant atoms or groups. Theaddition of pendant groups with oxygen bonds including carbonyls,hydroxyls, and carboxyls can have the effect of introducing some UVCabsorption but in some embodiment it can be preferred over monomers withhalogen pendant groups because of improved adhesion, cost benefits, orthe like.

In another example, the polymer binder can include polymers made from ablend of monomers. The blended polymer binder can include both organicand inorganic polymers. An example of an inorganic polymer includespolydimethylsiloxane. In another example, the polymer binder can includesubstantially all inorganic polymers, including examples where noorganic monomer is present in the polymer binder.

The polymer binder can include polymers made from more than one monomer.The polymer binder can include more than one polymer blend. The bindercan include more than one binder type including organic and inorganicbinders.

Using the teaching describe herein, one skilled in the art can makecoatings with polymer binders that can include, but are not limited to,alkyds, acrylics, vinyl-acrylics, vinyl acetatelethylene (VAE),polyurethanes, melamine resins, epoxies and some oil resins. It shouldbe noted that many of the polymer binder examples listed above canbecome unsuitable if they are modified with aromatic groups, which is acommon copolymer structure of many of the binders both within the chainstructure and as a pendant group.

Viscoelastic properties of the binder can be selected based on a desiredapplication, such as a substrate material the UVC reflective coating isto be applied. For example, a more flexible polymer binder can includeglass transition temperatures (Tg) lower than about 20 degrees Celsius(° C.) or lower can be selected for fabrics, while a polymer binder withTg higher than about 25° C. or higher can be selected for rigidsurfaces, such as a floor, a wall, a ceiling, or the like. The minimalfilm formation temperature (MITT) of the formulated coating can be lowerthan the application temperature.

Inorganic Material

Inorganic materials can include what are generally referred to aspigments. Inorganic materials and pigments can include granular solidsincorporated in the coating to contribute opacity or color. Inorganicmaterials (e.g., pigments) that may be suitable for UVA reflectingcompositions can be absorbing at UVC. Examples of pigments known for atleast partial UVA reflection include zinc-containing inorganics andantimony trioxide, both of which at least partially absorb UVC. Further,fewer inorganics are suitable pigments for UVC reflecting less-than-CPVC(e.g., non-void) coatings. Preferred inorganics include sub-microninorganics which are at least partially transparent at UVC wavelengths.Further, preferred inorganics include those which also have an index ofrefraction which is different from than that of the binder by at leastabout 0.2. In an example, the inorganic material can have an index ofrefraction at least about 0.3, 0.4, 0.5, 0.7, 1.0, 1.2, 1.4, 1.6, 1.8,2.0, 2.2, 2.4 or greater. In an example, the inorganic material and thebinder can have an index of refection difference of at least about 0.3,0.4, 0.5, 0.7, 1.0, 1.2, 1.4, 1.6 or greater.

In an example, the inorganic material can have nearly homogenous crystalstructures. For example, the inorganic material can a have purity levelsuch that at least about 90 wt %, 91 wt %, 92 wt %, 93 wt %, 94 wt %, 95wt %, 96 wt %, 97 wt %, 98 wt % or 99 wt % or greater of the inorganicconstitutes UVC transparent crystals, and most preferably at least about99.9 wt %. In an example, the inorganic material can be substantiallydevoid of an impurity, such as titanium dioxide, zinc, lead, or UVCabsorbing materials. Substantially devoid can include something that isless than about 1 wt %, 0.5 wt % 0.2 wt %, 0.1 wt %, 0.01 wt % or lessof a total weight of the coating.

Those skilled in the art can identify those inorganic materials thatmeet the preferences described herein. Particles of the inorganicmaterial smaller than about 200 nm or less can be used when formulatingsemi-transparent (e.g., human-visible wavelengths) compositions.Inorganic materials can include, in an example, an average particle sizeof about 10 nm to about 500 nm. The refraction index of the inorganicmaterial relative to the binder can also affect optimal particle sizingfor both human-visible transparent and opaque UVC reflective coatings.

In an example, the inorganic material can include a pure form, an oxideform, a nitride form or an oxynitride form, of at least one of the groupconsisting of magnesium, aluminum, tantalum, titanium, holmium, calcium,lanthanum, germanium, tellurium, europium, erbium, neodymium, samarium,ytterbium, gold, silver, and zirconium. In an example, the inorganicmaterial can include any of the group consisting of magnesium oxide,aluminum oxide, tantalum oxide, titanium oxide, holmium oxide, hafniumoxide, calcium oxide, lanthanum oxide, germanium oxide, tellurium oxide,zirconium oxide, europium oxide, erbium oxide, neodymium oxide, samariumoxide, ytterbium oxide, gold oxide, and silver oxide.

Refractive Index

The present inventors have determined that common refractive indexvalues for coating materials are not accurate for UVC reflectiveapplication unless those refractive index values are measured at the UVCwavelengths. However, refractive index differences between phases andparticles can be experimentally determined. That is binders, additives,and pigments, such as the inorganic material, can be separately studiedfor their UVC absorbance, reflectance, fluorescence, or transmissionproperties. The coating composition materials can be experimentallycharacterized for their UVC properties at a specific band of lightwithin UVC for the application. For example, in a UVGI application thespecific band can be around 254 nm.

Additives

The UVC reflective coating can include a wide variety of additives,which can be added in small amounts, but provide a measureable effect onthe coating. Some examples can include additives to modify surfacetension, improve flow properties, improve the finished appearance,increase wet edge, improve pigment stability, impart antifreezeproperties, control foaming, control skinning, or the like. Other typesof additives can include catalysts, thickeners, stabilizers,emulsifiers, texturizers, adhesion promoters, UV stabilizers, flatteners(e.g., de-glossing agents), biocides to fight bacterial growth, and thelike.

Additionally, the coating can include filler, such as granular solidsincorporated to impart toughness, texture, give the coating desiredproperties, or to reduce the cost of the coating. Fillers can include atype of pigment that serves to thicken the film, support its structureand increase the volume of the coating. Fillers are usually relativelyinexpensive and inert materials, such asdiatomaceous earth, talc, lime,barytes, clay, or the like.

Coating

The UVC reflective coating of the present disclosure can be below CPVC.That is, the UVC reflective coating can include a non-void coating.Previous approaches to UVC reflective coatings can include non-metal andmetal approaches. Non-metal approaches can achieve UVC reflectionthrough light-scattering air voids, such as void coatings. Coatingsrelying on void scattering can use high loadings of pigments, such aschalk (e.g., calcium carbonate), gypsum (e.g., kalsomine), bariumsulfate and other low refractive index materials. At high loadings(e.g., greater than CPVC) of otherwise transparent extender pigments,air voids can form in the coating as it dries due to poor binder wettingof the pigment particles and the packed nature of those particles. Therefractive index difference between air and the pigment, or the air andthe binder, can create the light scattering needed for opacity andreflection. Such void coatings with greater than CPVC compositions whoselight scattering can be prone to staining, suffer from low gloss, becomepartially transparent when wet (due to water filling the air voids),have poor rub resistance and other poor performance properties. Thepresent UVC reflective coating can include a non-void coating capable ofmitigating or eliminating at least one of these performance issues ofprevious coatings.

The present UVC reflective coating can be human-visible transparent,translucent (e.g., semi-opaque), or fully opaque, depending upon thedesired end-use or substrate the UVC reflective coating is to be appliedto. For example, healthcare facilities can have a variety of wallsurfaces including traditional drywall based or brick painted surfaces,as well as fabric, polymer or paper wall coverings, glass surfaces, woodand metal doors, or polymer, metal, or fibrous ceiling tiles andceramic, carpeted, or wood or polymer floor material. In the case of atextured, colored, or fabric wall covering, the UVC reflective coatingmay be desired to be human-visible transparent to reduce the effect onthe aesthetic appearance of the existing wall. The UVC reflectivecoating can be incorporated into the wall, ceiling, or floor material atthe manufacturer, such as during or after the manufacturing of the wall,ceiling, or floor material.

In an example, the UVC reflective coating can be human-visibletransparent, such as including high index of refraction UVC scatteringparticles (e.g., the inorganic material) with an average particle sizebetween about 10 to about 180 nm in conjunction with UVC transparentbinders and additives. In another example, the UVC reflective coatingcan have a degree of opacity, such as including a generally largeraverage particle size of UVC scattering particles (e.g., the inorganicmaterial), such as from about 180 nm to about 1 micron nm or larger. Inan example, the generally larger average particle size UVC scatteringparticles can be used in a coating with UVC transparent binders andadditives.

The UVC reflective coating of the present disclosure can be water based,such as a latex emulsion. In an example, the UVC reflective coating canbe solvent borne, such as an oil based coating. Coatings can be crosslinked by mixing or with added heat or other energy source. Variouscoatings utilizing pigment-binder-additive building blocks can beformulated to be UVC reflective according to the present disclosure,such that the UVC reflective coatings can be suitable for applicationssuch as UVGI.

In an example, the UVC reflective coating can reflect at least about 10%of incident UVC light. That is, the UVC reflective coating, such asapplied to a surface, can reflect at least 10% of the UVC light photonsthat contact the UVC reflective coating. Further, in an example, the UVCreflective coating can reflect up to about 75%, about 80%, about 82%,about 85%, about 87% or about 90% or more of incident UVC light. The UVCreflective coating composition can be designed according to a designatedapplication. For example, in a hospital room application, high levels ofUVC reflection, such as about 50% or greater, can be desired to provideincreased sterilization potential. In such an application, a specifiedinorganic material, amount (e.g., volume, weight) of the specifiedinorganic material, a specified polymer binder, amount (e.g., volume,weight) of the specified polymer binder, or amount or type of additivecan be specified to provide the desired UVC reflectivity.

Enumerated Embodiments

Specific enumerated embodiments [1] to [27] provided below are forillustration purposes only, and do not otherwise limit the scope of thedisclosed subject matter, as defined by the claims. These enumeratedembodiments encompass all combinations, sub-combinations, and multiplyreferenced (e.g., multiply dependent) combinations described therein.

[1.] An ultraviolet light-C (UVC) reflective coating composition,including:

a polymer binder of a first volume having a first refractive index; and

an inorganic material of a second volume having a second refractiveindex at least 0.2 greater than the first refractive index, the secondvolume in ratio to the first volume such that the reflective coating isat or below critical pigment volume concentration (CVPC), wherein thereflective coating is configured to diffusely reflect at least 10% UVC.

The UVC reflective coating of embodiment 1, wherein the coating issubstantially devoid of an inorganic binder.

[3.] The UVC reflective coating of anyone or all of the aboveembodiments, wherein the coating is substantially devoid of anon-polymer inorganic binder.

[4.] The UVC reflective coating of anyone or all of the aboveembodiments, wherein the coating is substantially devoid of titaniumdioxide.

[5.] The UVC reflective coating of anyone or all of the aboveembodiments, wherein the coating is substantially devoid of includezinc.

[6.] The UVC reflective coating of anyone or all of the aboveembodiments, wherein the coating is substantially devoid of lead.

[7.] The UVC reflective coating of anyone or all of the aboveembodiments, wherein the inorganic material includes an average particlesize less than a micron.

[8.] The UVC reflective coating of anyone or all of the aboveembodiments, wherein the inorganic material includes an average particlesize is from about 200 nm to about 800 nm.

[9.] The UVC reflective coating of anyone or all of the aboveembodiments, wherein the inorganic material has a particle size of about10 nanometers to about 500 nanometers.

[10.] The UVC reflective coating of anyone or all of the aboveembodiments, wherein the inorganic material has a particle size lessthan about 180 nanometers.

[11.] The UVC reflective coating of anyone or all of the aboveembodiments, wherein the inorganic material is a metal oxide.

[12.] The UVC reflective coating of anyone or all of the aboveembodiments, wherein the inorganic material is at least one of magnesiumoxide, aluminum oxide, tantalum oxide, holmium oxide, hafnium oxide,calcium oxide, lanthanum oxide, germanium oxide, tellurium oxide,zirconium oxide, europium oxide, erbium oxide, neodymium oxide, samariumoxide, yttrerbium oxide, gold oxide, and silver oxide.

[13.] The UVC reflective coating of anyone or all of the aboveembodiments, wherein the inorganic material at least one of a pure form,an oxide form, a nitride form or an oxynitride form, of at least one ofthe group consisting of magnesium, aluminum, tantalum, holmium, calcium,lanthanum, germanium, tellurium, zirconium, europium, erbium, neodymium,samarium, ytterbium, gold, and silver.

[14.] The UVC reflective coating of anyone or all of the aboveembodiments, wherein the inorganic material has a purity level of atleast 99% UVC transparent crystals.

[15.] The UVC reflective coating of anyone or all of the aboveembodiments, wherein the inorganic material has a purity level of atleast 99.9% UVC transparent crystals.

[16.] The UVC reflective coating of anyone or all of the aboveembodiments, further including a colorizing pigment.

[17.] The UVC reflective coating of anyone or all of the aboveembodiments, further including an additive configured to aid insuspending the inorganic material within the coating composition.

[18.] The UVC reflective coating of anyone or all of the aboveembodiments, wherein the polymer binder includes an aliphatic compound.

[19.] The UVC reflective coating of anyone or all of the aboveembodiments, wherein the polymer binder includes at least one monomerincluding a pendant group.

[20.] The UVC reflective coating of anyone or all of the aboveembodiments, wherein the polymer binder includes at least one monomerwith a halogenated element.

[21.] The UVC reflective coating of anyone or all of the aboveembodiments, wherein the polymer binder includes at least one monomerwith a non-chlorine halogenated element.

[22.] The UVC reflective coating of anyone or all of the aboveembodiments, wherein the polymer binder includes polyvinylidenefluoride.

[23.] The UVC reflective coating of anyone or all of the aboveembodiments, wherein the second refractive index is at least 0.5 greaterthan the first refractive index.

[24.] The UVC reflective coating of anyone or all of the aboveembodiments, wherein the UVC reflective coating is at least partiallyhuman vision transparent.

[25.] The UVC reflective coating of anyone or all of the aboveembodiments, wherein the UVC reflective coating is at least partiallyhuman vision opaque.

[26.] The UVC reflective coating of anyone or all of the aboveembodiments, wherein the UVC reflective coating is configured to reflectat least 40% UVC light at 254 nm wavelength.

[27.] The UVC reflective coating of anyone of all of the aboveembodiments, wherein the polymer binder is an organic binder.

EXAMPLES Example 1

A coating containing a blend of polyvinylidiene fluoride and polymethylmethacrylate at a ratio of fifty-fifty, in an emulsion with 15%coalescing solvent by weight of hinder solids, with 300 nm 99.9% purehafnium oxide particles in a dispersion at 70% solids by weight with 3%nonionic surfactant, said dispersion added to the emulsion at 1 partdispersion to 2 parts emulsion.

Example 2

A coating containing a blend of polyvinylidiene fluoride and polymethylmethacrylate and polyethylene acetate at a ratio of 1 to 1 to 2, in anemulsion with 12% coalescing solvent by weight of binder solids, with500 nm 99.9% pure hafnium oxide particles and 900 nm 99% pure aluminumoxide particles at a ratio of 1 to 2 in a dispersion at 70% solids byweight with 3% nonionic surfactant and 1% steric stabilizer, saiddispersion added to the emulsion at 1 part dispersion to 3 partsemulsion.

Example 3

A coating containing a blend of poly(co-ethylene-co-vinyl acetate) andpolydimethylsiloxane at a ratio of 1.5 to 1, in an emulsion with 9%coalescing solvent by weight of binder solids, with 1.2 micron 99.9%pure magnesium oxide particles and 500 nm 99% pure aluminum oxideparticles at a ratio of 1 to 3 in a dispersion at 65% solids by weightwith 3% nonionic surfactant and 1% steric stabilizer, said dispersionadded to the emulsion at 1 part dispersion to 2.1 parts emulsion.

All publications, patents, and published patent applications disclosedherein are incorporated herein by reference in their entirety. While inthe foregoing specification this invention (as defined by the issuedclaims) invention has been described in relation to certain preferredembodiments thereof, and many details have been set forth for purposesof illustration, it will be apparent to those skilled in the art thatthe invention is susceptible to additional embodiments and that certainof the details described herein may be varied considerably withoutdeparting from the basic principles of the invention.

What is claimed is:
 1. An ultraviolet light-C (UVC) reflective coatingcomposition, comprising: a first material, wherein the first materialincludes a polymer binder and has a first volume and has a firstrefractive index; and a second material, wherein the second material isnot an organic material and has a second volume and has a secondrefractive index that is different from the first refractive index by afactor of at least 0.2, wherein the second volume in ratio to the firstvolume such that the reflective coating is at or below critical pigmentvolume concentration (CPVC), wherein the reflective coating isconfigured to diffusely reflect at least 10% UVC, and wherein the secondmaterial is at least partially transparent to light at UVC wavelengths.2. The UVC reflective coating of claim 1, wherein the coating issubstantially devoid of an inorganic binder.
 3. The UVC reflectivecoating of claim 1, further comprising a colorizing pigment.
 4. The UVCreflective coating of claim 1, further comprising an additive configuredto aid in suspending the second material within the coating composition.5. The UVC reflective coating of claim 1, wherein the polymer binderincludes at least one monomer with non-chlorine halogenated elements. 6.The UVC reflective coating of claim 1, wherein the polymer binder isaliphatic.
 7. The UVC reflective coating of claim 1, wherein the secondmaterial includes an average particle size less than 1.0 micron.
 8. TheUVC reflective coating of claim 1, wherein the second material has aparticle size of at least about 10 nanometers.
 9. The UVC reflectivecoating of claim 1, wherein the second material has a particle size ofless than about 800 nanometers.
 10. The UVC reflective coating of claim1, wherein the second material is a metal oxide.
 11. The UVC reflectivecoating of claim 1, wherein the second material is any of the groupconsisting of magnesium oxide, aluminum oxide, tantalum oxide, holmiumoxide, hafnium oxide, calcium oxide, lanthanum oxide, germanium oxide,tellurium oxide, zirconium oxide, europium oxide, erbium oxide,neodymium oxide, samarium oxide, yttrerbium oxide, gold oxide, andsilver oxide.
 12. The UVC reflective coating of claim 1, wherein thesecond material is a pure form, an oxide form, a nitride form or anoxynitride form, of at least one of the group consisting of magnesium,aluminum, tantalum, titanium, holmium, hafnium, calcium, lanthanum,germanium, tellurium, zirconium, europium, erbium, neodymium, samarium,ytterbium, gold, and silver.
 13. The UVC reflective coating of claim 1,wherein the second material has a purity level of at least 99 wt % UVCtransparent crystals.
 14. The UVC reflective coating of claim 1, whereinthe second refractive index is at least 0.5 times greater or lesser thanthe first refractive index.
 15. The UVC reflective coating of claim 1,wherein the UVC reflective coating is at least partially human-visibletransparent.
 16. The UVC reflective coating of claim 1, wherein the UVCreflective coating is at least partially human-visible opaque.
 17. TheUVC reflective coating of claim 1, wherein the UVC reflective coating isconfigured to reflect at least 40% UVC light at 254 nm wavelength. 18.The UVC reflective coating of claim 1, wherein the polymer binder is anorganic binder.
 19. The UVC reflective coating of claim 1, wherein thesecond material is an inorganic material.